Bumper structures to absorb shocks at the time of impact are mainly equipped on the front and rear of an automobile. The bumper structure generally includes a reinforcement and an impact absorbing member. The bumper structure receives a shock at the reinforcement, and has a structure that suppresses damage to the car body by deformation of an energy absorbing member that absorbs the impact energy.
Many materials and shapes for improving the impact absorbing performance of energy absorbing members have been developed so far.
Patent Literature 1 discloses an energy absorbing member formed as an aluminum extruded member that has a cruciform inner wall having a substantially quadrangular cross section in a direction of compression and connecting two pairs of outer walls, wherein a portion connecting the outer walls and the inner wall is an internal projection.
Patent Literature 2 discloses a shock absorbing member structure which has a substantially quadrangular cross section and in which an internally projecting portion is disposed at an outer wall having a substantially quadrangular shape, and which is formed in such a way that adjustment of a plastic moment allows the shock absorbing member to repeatedly buckle and deform even when an oblique load is applied thereto.